Add pact templates for common commitments

[vayungodara]

Problem

Users must create every pact from scratch. This adds friction, especially for common goals like 'Exercise 3x/week' or 'Read 30 min/day'.

What to change

• Create a template library with 10-15 common pact templates organized by category (fitness, learning, productivity, wellness)
• Add a 'Use Template' button in components/CreatePactModal.js that pre-fills the form
• Allow users to customize templates before creating
• Optionally allow users to save their own pacts as templates

Files to modify

• components/CreatePactModal.js
• New: template data file (e.g., lib/pactTemplates.js)
• Possibly new UI component for template picker

Impact

Reduces friction for new users. Faster pact creation.

Effort

~3-4 hours

[vayungodara]

Closing as duplicate — kept the more detailed version.

[vayungodara]

Closing as duplicate of #20